lnterleukin-1(IL-1)(alpha is a pro-inflammatory cytokine produced by keratinocytes after chemical and physical stimulation. Because inflammation and sustained epidermal hyperplasia are essential components of the tumor promotion stage of mouse skin carcinogenesis, we propose to elucidate the role of IL-1alpha in skin carcinogenesis. Our hypothesis is that the induction of IL-1alpha is required for specific effects of tumor promoters and that IL-1 itself can elicit some of these effects. Studies designed to answer the following questions: (1) What changes occur in the expression of IL-1alpha, its receptor and receptor antagonist after single and multiple treatment with tumor promoters and in specific stages of carcinogenesis? mRNA levels, protein product, receptor number and affinity, and receptor antagonist expression will be determined in skin treated TPA, anthralin, or thapsigargin and in tumors at various stages of promotion and progression. (2) Does IL-1alpha induce proliferation and/or other pro-inflammatory agents in keratinocytes or mediate these tumor promoter-elicited responses? The effect of IL-Ia on DNA synthesis, proliferation related genes and other pro-inflammatory agents, will establish whether or not IL-1alpha alters keratinocyte behavior in a direct or autocrine manner. (3) How is IL-1alpha regulated by tumor promoters or itself, and how is the positive feedback loop controlled? To determine the mechanisms by which the IL-1 system is regulated the following areas will be elucidated: (i) regulation of IL-Ia by tumor promoters; (ii) autocrine regulation via IL-1alpha binding to its own receptor and elucidation of the signal transduction pathways involved; (iii) determining whether IL- 1alpha alters the level of receptors or receptor antagonist to shutdown an otherwise continuous feedback loop, and; (iv) modulation of IL-1alpha expression by eicosanoids, using eicosanoid inhibitors or specific eicosanoids. (4) What are the dermal responses to IL-1alpha and is IL-1 required for or contribute to tumor promoter-elicited hyperplasia and inflammation? The paracrine actions of IL-1alpha will be determined including inflammation and indirect effects on keratinocyte DNA synthesis. In vivo studies will employ tumor promoter treated or IL-1alpha injected skin in conjunction with anti-IL-1alpha antibody or IL-1 receptor antagonist. To further establish a paracrine role for IL-1alpha, in vitro studies designed to assess whether IL-1alpha stimulate dermal cells (fibroblasts, macrophages or endothelial cells) to secrete factors mitogenic to keratinocytes. (5) Is elevated IL-1 necessary for or contribute to tumor development? The requirement for IL-1alpha in tumor promotion will be assessed in tumor experiments using IL-1alpha, receptor antagonist and/or antibodies against IL-1alpha To determine whether the apparent constitutive high IL- 1alpha production by papillomas and carcinomas contributes to tumor growth, papilloma and carcinoma cell lines will be transfected with anti- sense IL-1alpha and transplanted into mice.